Henry george prested



No. 749,500. 7 PATENTED JAN. 12, 1904. H. G. PRESTBD. MINERS ELECTRICLAMP.

APPLIOATION FILED FEB. '7, 1903.

N0 MODEL.

DETECTOR ,M a

OFF N OFF 2 AT 0N Patented January 12, 1904.

PATENT OFFICE.

HENRY GEORGE PRESTED, OF CAMDEN TOWN, ENGLAND.

MINERS ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 749,500, dated January12, 1904:.

Application filed February '7, 1903. Serial No. 142,406. (No model.)

To all whom it may concern.-

Be it known that I, HENRY GEORGE PEEs'rED, a citizen of England,residing at 14: Brecknock road, Camden Town, in the county of London,England, have invented a certain new and useful Improved Miners ElectricLamp, (for whichI have applied for a patent in Great Britain, dated June21, 1902, No. 14,112,) of which the following is a specification.

My invention relates to a miners electric lamp the light of whichbecomes dim or is extinguished when the atmosphere contains combustiblegas.

It has frequently been suggested to make a fire-damp indicator by takingadvantage of certain properties of marsh-gas to close an electriccircuit, and thus give an indication by an electrical audible or visiblesignal. To all such devices, however, there is the serious objectionthat they can only be an adjunct to the miners lamp. What is required bythe miner or other user of a safety-lamp is alamp which, like thewell-known Davy lamp, will indicate the presence of the combustible gasby the dimming or even extinction of the light and at the same time maybe retained in the explosive atmosphere Without danger. Such a lamp hasthe great advantage that its indication cannot fail to be noted, becausethe user is sure to become aware of the diminution or extinction of thelight by which he works.

By my invention I take advantage of the fact that combustible gasdiffuses through a porous diaphragm at a rate different from that atwhich air difltuses. I apply this phenomena by making it move a contactto short-circuit the glowing lamp or to break the circuit thereof.

In the accompanying drawings, Figure 1 is an elevation of a miners lamphaving my improvements applied thereto. Fig. 2 is a sectional plan online 2 2 of Fig. 1. Fig. 3 is an elevation of the box a, the casing ahaving been removed; and Fig. 4 is a section on the line i 1 of Fig. 2,the switch-spindle having been turned through an angle of ninetydegrees.

Referring to Figs. 1 to 4:, I mount a box a on a suitable case Z),containing an electric battery the terminals of which are connected 7with terminals 0 and (Z, respectively. The conducting-spindle c of theswitch f has two opposite notches e c in its periphery. I/Vhcn theswitch is in the position shown in Figs. 1, 2, and 3, the spindle c isin contact with both the conducting-springsf f. The former, f", of theseis in connection with terminal csay, the positive terminalof thebattery. The spring f is in connection with a contact 1, best ofplatinum or the like, carried by a flexible diaphragm it, which covers ahole in the side of the box a. Fastened to the front of the box (0 is aspring 2', carrying a point z", of platinum or the like, the distancebetween this point and the contact on the diaphram being adjustable by aset-screw i. When, as shown in Fig. '2, there is no contact between thepoint t" and the contact g, the path of the current is from 0 throughspring f, spindle e, lamp-terminal K1, the lamp, lamp-terminal Z, toterminal (Z. The lamp thus receives the full current and illuminates theminers work. Now at the back of the box a is a perforated plate (6protecting a diflusion-plate (0 so that when the lamp is brought into anatmosphere containing a gas lighter than air the pressure within the boxis increased by diffusion of that gas into the box faster than the aircan diffuse out. Thus the diaphragm it is bulged outward and contact ismade between 9 and i. The current has now another path open toit-namely, from 0 through spring f, spring f contact g, spring 2',lamp-terminal Z, to terminal (Z. This portion of the current does notflow through the lamp, so that this latter becomes dim or evenextinguished, according to the relative resistances of the two circuits.In order to cut out the indicator, it is only necessary to turn thespindle 0 into the position shown in Fig. 4c, in which the notch breakscontact between spring f and the spindle. All the current now flowsthrough the lamp whether contact exists between 9 and c" or not, and theindicator is therefore inefl'ective. The third position of the switch isthat in which notch e breaks contact between spring f and spindle e. Thecurrent is then switched off altogether from the lamp.

Having thus described the nature of this invention and the best means Iknow of carrying the same into practical effect, I claim 1. A minerselectric lamp comprising a diffusion device, a lamp and a circuitshort-circuiting the lamp so as to render the latter useless when thesaid diffusion device is in action, substantially as described.

2. A miners electric lamp comprising a diffusion device, a circuitshort-circuiting the lamp when the said device is in action and a switchwhich in one position cuts out the said circuit while still supplyingcurrent to the lamp, substantially as described.

3. In a miners electric lamp the combination of a chamber, a porous wallto such chamber, a movable diaphragm covering an opening in suchchamber, an electrical contact carried by such diaphragm, an electriccircuit completed by such contact when the said diaphragm is moved, anda switch for throwing said lamp and diaphragm out of circuit and thelamp into circuit when said switch is turned in one position,substantially as described.

4C. In a miners electric lamp the combination of a chamber, a porouswall to such chamber, a movable diaphragm covering an opening in suchchamber, an electrical contact carried by said diaphragm, an electriccircuit completed by such contact when said diaphragm is moved, and adouble-acting switch arranged to throw the contact and diaphragm intocircuit with the lamp, and when turned into another position to cut saidcontact and diaphragm out of circuit and throw said lamp into a directcircuit, substantially as described,

5. In a miners electric lamp the combination of a chamber, a porous wallto such chamber, a movable diaphragm covering an opening in suchchamber, an electrical contact carried by said diaphragm, a contactnormally out of engagement with the diaphragm, a circuit including saidcontacts and lamp, a branch circuit passing through the lamp alone, aswitch which in one position cuts out the said contacts and applies thecurrent directly to the lamp through the branch circuit and when turnedto another position breaks both said circuits, substantially asdescribed.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

HENRY GEORGE PRESTIED. WVitnesses:

EDWARD GARDNER, WV ALTER J. SKERTEN.

